other time...can't get date

[Lykurg]

Then something with your label is not right.

QDateTime dias;
    dias.setTime_t(1003030900);
    QLabel l;
    l.setText(dias.toString("yyMMddhhmm"));
    l.show();

QDateTime dias;
    dias.setTime_t(1003030900);
    QLabel l;
    l.setText(dias.toString("yyMMddhhmm"));
    l.show();

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works perfect. See if dias is valid where you want to use it. It seems to me your code confuses allocation on the heap and stack. Show us a little more code.